1. Field of the Invention
The present invention relates to an indexable cutting insert made of a tungsten carbide-polycrystalline-tungsten carbide composite wafer material wherein the tungsten carbide is ground to form a chip breaker and thereby reveal the polycrystalline material for use as a cutting edge. The polycrystalline material may be diamond, cubic boron nitride (cBN), or any other suitable polycrystalline material.
The present invention further relates to the use of a polycrystalline composite material as a cutting insert which does not have to be bonded or brazed or otherwise affixed to an insert body.
2. Description of the Related Art
Noggle, U.S. Pat. No. 5,193,948 discloses a cutting insert having a pocket formed at one corner of the insert and a wafer of tungsten carbide-polycrystalline-tungsten carbide bonded thereto. The top surface of the wafer is ground away to form a chip breaker and to expose a polycrystalline diamond cutting surface.
The insert of Noggle '948 is not truly indexable unless a pocket is formed in each corner of the insert body and a wafer is bonded into the pocket to provide the polycrystalline cutting edge. Moreover, forming multiple pockets and bonding polycrystalline wafers thereto is expensive and time consuming. Thus, where indexablity is required, there was a long felt need.
Murray et al., U.S. Pat. No. 4,854,784 discloses a diamond tipped chip control insert which incorporates a polycrystalline diamond or cubic boron nitride material therein as a cutting edge material. The insert substrate includes integral chip control features which eliminate the need for the use of separately attached mechanical chip breakers.
Murray et al., '784 differs from the present invention because Murray requires that a chip breaker first be formed and then a slot is cut into the insert body and a polycrystalline material is finally bonded into the slot. This arrangement is expensive, labor intensive, and does not provide true indexability of a polycrystalline cutting edge.
Jurgens, U.S. Pat. No. 4,498,549 discloses a cutting member for a rotary drill bit comprised of a substrate to which is bonded a polycrystalline material. The drill does not have any chip breaker features and neither does it utilize the tungsten carbide-polycrystalline-tungsten carbide wafer of the present invention.
Bibbs, Jr. et al., U.S. Pat. No. 4,605,343 discloses a sintered polycrystalline diamond compact having an integral metallic heat sink bonded to and covering at least the outer diamond surface. The metallic heat sink is used to increase compact life when the compact is used for material removal without fluid coolant. The present invention does not require a metallic heat sink to achieve dry cutting. In addition, the present invention provides for a chip breaker as well as indexablity of the insert such that polycrystalline material is present at the cutting edge of the insert.
Slutz et al., U.S. Pat. No. 4,899,922 discloses a brazed thermally stable polycrystalline diamond compact having a network of interconnected empty pores dispersed throughout the compact and bonded to a substrate by brazing filler metal which may be an alloy having a liquidus above about 700 degrees C. Slutz et al., '922 is directed to the manner in which the polycrystalline material is bonded to the insert. There is no showing in Slutz et al., '922 of using a polycrystalline wafer as a metal cutting insert having indexability.